Capacitive infrared detectors are known in the art that use a ferroelectric capacitor element. The dielectric constant of the material between the plates of a conventional ferroelectric capacitor varies with temperature. U.S. Pat. No. 3,073,974, issued to S. Hoh, is an early example of the application of ferroelectric physics to the problem of energy conversion. Conventional infrared capacitive detectors using the ferroelectric principle are illustrated in U.S. Pat. No. 4,080,532, issued to G. Hopper, and U.S. Pat. No. 4,250,384, issued to C. Pulvari.
These conventional or "voltage mode" infrared detectors suffer from two disadvantages. In general, responsivity of these detectors to temperature change is low, causing sensitivity to be limited by readout preamplifier noise. Also, a chopper has conventionally been required. The chopper presents a scene of uniform temperature to the ferroelectric sensing elements, such that they can be "zeroed" for the next scene using the temperature of the chopper. The requirement of a chopper results in increased mechanical complexity and a 50% loss of signal, as the chopper must be interposed between the field and the sensing elements each time a new image is to be recorded.
In view of the above, a need exists to provide a capacitive infrared bolometer that does not require a chopper, thus reducing mechanical complexity. Further, a need exists to provide a capacitive infrared bolometer that has increased responsivity to changes in scene temperature.